During the extensive laboratory renovations following our move to Bldg. 5, there was a complete change in laboratory personnel. For most of the year, only one visiting fellow was present. These events temporarily slowed our progress towards understanding the molecular biology of vertebrate DNA repair. During early development Xenopus replicates its DNA nearly as fast as E. coli in log phase. We demonstrated that oocytes are an excellent source of both DNA repair activity and single-strand to double-strand replication activity. Pyrimidine dimer and (6,4) photoproduct repair was shown by microinjecting UV-irradiated plasmid DNA into oocytes or adding damaged DNA to an extremely efficient extract derived from oocytes. We have also studied DNA repair for alkylated and chemically modified DNA as well as DNA replication with our repair extract. One of the advantages of the Xenopus system is that we can study repair/replication reactions both in living cells by microinjection and in extremely efficient extracts. Unlike other extracts that repair <2% of the input damaged DNA, our extracts repair all of the damaged substrate.